全新java初学者实践教程6(Java SE5.0版)
kO/]mNLG 基本语法3
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<HUU 2#)z%K6T ioJ|-@!#o 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
#,CK;h9jy! "|nh=!L [font="Times] 1.循环语句[font="Times]:while,do-while,for
SL5QhP fjh,e [font="Times]2.分支语句[font="Times]:if-else,switch,
4 zhg# [font="Times]
<*[D30< 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
mRT$@xa]J [font="Times]
^{g('BQx 4.异常处理语句[font="Times]:try-catch-finally,throw
"Ta"5XW *o6hDhg 实践:
`EWQ>m+ [font="Times] 1.循环语句
BFvRU5&Sz [font="Times] while 语句
Pq3m(+gf [font="Times]class While {
%4^NX@1jV [font="Times]public static void main(String args[]) {
|3P dlIbO [font="Times]int n = 10;
sh)[|?7z [font="Times]while(n > 0) {
k] iyx [font="Times]System.out.println("tick " + n);
oef] [font="Times]n--;
<~}NxY\5 [font="Times]}
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H6Q!~o\"H [font="Times]}
K+3+?oYKH [font="Times] do…while 语句
}e]tn) [font="Times] class DoWhile {
|32uC3?o [font="Times]public static void main(String args[]) {
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HRfTF [font="Times]int n = 10;
EYSBC", [font="Times]do {
:CGh$d] + [font="Times]System.out.println("tick " + n);
Ci$?Hm9 n [font="Times]n--;
bsv!z\} [font="Times]} while(n > 0);
]S7>=S [font="Times]}
NudY9~ [font="Times]}
yn|U<Hxl~H 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
!EOYqD [font="Times] for语句
JmF:8Q3H [font="Times] class ForTick {
]/[$3rPwZ [font="Times]public static void main(String args[]) {
c"oJcp [font="Times]int n;
e)f!2'LL [font="Times]for(n=10; n>0; n--)
S<81r2LT [font="Times]System.out.println("tick " + n);
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qZYh^\ [font="Times]}
a\*_b2 ^n 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
(w1$m8`= 还有啊,[font="Times]for循环的部分可以为空的
s(pNg?R [font="Times]class ForVar {
d8J(~$tXQN [font="Times]public static void main(String args[]) {
n+D93d9LP [font="Times]int i;
[!Zyp`: [font="Times]boolean done = false;
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El',gY [font="Times]i = 0;
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[font="Times]for( ; !done; ) {
/|p6NK;8L [font="Times]System.out.println("i is " + i);
-Ra-Ux [font="Times]if(i == 10) done = true;
/3j3'~0 [font="Times]i++;
dmPAPCm%y [font="Times]}
s|D[_N!| [font="Times]}
&Ivf!Bgm{Z [font="Times]}
循环语句的例子下载 -+fW/Uo [font="Times] 2.分支语句[font="Times]
k{J\)z [font="Times] if/else语句
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[font="Times]class IfElse {
>l^[73,]L [font="Times]public static void main(String args[]) {
&0RKNpwg [font="Times]int month = 4; // April
.f9&.H# [font="Times]String season;
j5!pS xOC [font="Times]if(month == 12 || month == 1 || month == 2)
=y0h\<[ [font="Times]season = "Winter";
M.``o1b [font="Times]else if(month == 3 || month == 4 || month == 5)
K$c?:?wmo [font="Times]season = "Spring";
!|~yf3 [font="Times]else if(month == 6 || month == 7 || month == 8)
A`nzqe#(1 [font="Times]season = "Summer";
u?SxaGEa [font="Times]else if(month == 9 || month == 10 || month == 11)
'}9 %12\^h [font="Times]season = "Autumn";
Q.g44> [font="Times]else
*T2kxN,Ik [font="Times]season = "Bogus Month";
09J,!NN [font="Times]System.out.println("April is in the " + season + ".");
e4<St`K [font="Times]}
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[font="Times]}
t#2szr+ [font="Times]//这段程序输出[font="Times]:
oT i$@q [font="Times]//April is in the Spring.
O |0V mm
[font="Times]// 注意[font="Times] “[font="Times]||”是或运算
6+/BYN!&4 [font="Times] switch语句
4VP$,|a [font="Times] class Switch {
.5!Q( [font="Times]public static void main(String args[]) {
`<(o;*&Gd [font="Times]int month = 4;
#{5h6IC [font="Times]String season;
gg@Ew4L& [font="Times]switch (month) {
I[KAW" [font="Times]case 12:
eE" *c>I [font="Times]case 1:
2`A\'SM'4 [font="Times]case 2:
AA5UOg\jI [font="Times]season = "Winter";
Bpp(5 [font="Times]break;
WDF6.i ? [font="Times]case 3:
x.>&|Ej [font="Times]case 4:
UV\&9>@L [font="Times]case 5:
HXgf=R/$ [font="Times]season = "Spring";
z6Zd/mt~x [font="Times]break;
P\&n0C~ [font="Times]case 6:
>:|jds# [font="Times]case 7:
7~H"m/;U& [font="Times]case 8:
ne# %Gr [font="Times]season = "Summer";
+HEL ^ [font="Times]break;
,'byJlw_pv [font="Times]case 9:
K~A@>~vFb [font="Times]case 10:
%<\tN^rP [font="Times]case 11:
Id{Ix(O [font="Times]season = "Autumn";
~;@\9oPpz% [font="Times]break;
yAQ)/u[| [font="Times]default:
G$t:#2 [font="Times]season = "Bogus Month";
R<Ct{f! [font="Times]}
vu3zZMl [font="Times]System.out.println("April is in the " + season + ".");
emG1Wyl [font="Times]}
9>ML;$T& [font="Times]}
分支语句代码下载 O
+Xu?W] P(B&*1X [font="Times]switch语句适合于条件非常多的逻辑
B3Ws)nF" 请看上述语句可以混合使用,请看
下载例子